As with any animal, water is very important to a horse's health. The horse must drink enough water to keep its body hydrated and enable it to perform essential life functions such as sweating and digestion. By knowing how much water a horse should drink, you can monitor your own horse and make sure that it's getting enough to keep it healthy.
According to Horse and Hound, a horse's body is nearly 70 percent water. This liquid is essential to the horse's life functions. Horses sweat to cool their bodies, and adequate consumption of water is needed to replenish the liquid lost through that process. Water is also essential to the digestive process. The majority of a captive horse's diet is made up of dry foods like hay and grain. If the horse doesn't drink enough water, it can suffer an impaction and develop colic, a life-threatening condition.
According to the Canadian Agri-Food Research Council, the average water consumption for horses is 4 1/2 gallons per day for a horse weighing 900 pounds, 6 gallons per day for a 1,200-pound horse and 8 galllons per day for a 1,500-pound horse. These numbers can vary somewhat and still be in the normal range. For example, a 1,200 pound horse might drink as little as 4 gallons a day or as much as 8 gallons a day. A 900-pound horse can drink between 3 and 6 gallons as a norm, and a 1,500-pound horse can drink between 5 and 10 gallons.
Many considerations affect how much water a horse will drink. These include the outside air temperature, the type of food the horse is eating, its health, and how much it is being worked. When it is hot, a horse will usually drink more than on days with a mild temperature. If the horse is eating a lot of dry food, such as grain and hay, it will drink more than it would if the majority of its diet were made up of moist, fresh grass. A horse that is being exercised regularly will drink more than one that stands around passively in its stall or pasture.
With most methods of providing water for a horse, you can monitor how much the horse is drinking. If you are giving the water in a bucket or trough, you can simply monitor the water level. If more than one horse is drinking from the same trough, this will make it harder to know how much each individual animal is drinking. If your horse drinks from an automatic water supplier in its stall, you will not be able to monitor how much it drinks. If the horse is sick or you need to monitor its water intake for some other reason, turn off the automatic water supply and temporarily replace it with a bucket.
If you cannot tell how much water your horse has consumed, you can test it for dehydration by pinching a fold of its skin together. The more slowly the skin returns to its normal shape, the more likely it is that your horse is dehydrated.
You can encourage your horse to drink more water by giving it access to a salt or mineral block. The horse will also drink more if it has continual access to a fresh, clean supply of water. You can accomplish this by cleaning and refilling the trough or water bucket whenever it gets dirty or the water has been out for more than a few hours.